The present invention generally relates to methods and systems for testing mobile communication systems, and more particularly to a method and a system for testing a mobile communication system such as a portable mobile radiotelephone (hereinafter simply referred to as radiophone) and an automobile telephone (hereinafter simply referred to as a carphone). The method and system according to the present invention is used for detecting a line abnormality in a monitoring control line between a line control station and a pseudo (or simulating) mobile station which is used for line testing.
In a mobile communication system, a test is made to determine whether or not a line connection is correctly carried out between a radio base station and a mobile station. When making the test, a line test instruction is sent from a line control station to a pseudo (or simulating) mobile station which is set up in the radio base station via a monitoring control line. A check is made to determine whether or not the pseudo mobile station correctly carries out a line connection responsive to the line test instruction. In this case, when an abnormality exists in the monitoring control line, the above described test cannot be made. For this reason, it is also necessary to monitor whether or not an abnormality exists in the monitoring control line. Of course, the line test instruction may be sent from the pseudo mobile station to the line control station so as to carry out a similar test.
FIG.1 shows an example of a conventional portable mobile radiotelephone system. This portable mobile radiotelephone system includes a public line network 1, a central control station 2, a radio base station 3 and mobile stations 4. The public line network 1 connects a general subscriber to the central control station 2 via a public line switching system 11. The central control station 2 includes a line switching part 21, a line control unit 22, a customer control and accounting system 23, a monitoring control unit 24 and the like. The radio base station 3 includes a radio unit 31, a monitoring control unit 32, a testing fixed station 33 and the like. The testing fixed station 33 has the same calling means as the mobile stations 4. The monitoring control unit 24 of the central control station 2 and the monitoring control unit 32 of the radio base station 3 are connected by a monitoring control line 61. Hence, test instruction information which is used for testing a message line (a line of a radio system) can be transmitted from the line control unit 22 to the testing fixed station 33.
In the portable mobile radiophone system shown in FIG.1, it is necessary to periodically monitor whether or not a message line between the general subscriber and the mobile station 4 is normal by carrying out a test. This test is carried out in the following manner.
First, in the central control station 2, a testing subscriber number and identification (ID) number are input and set from a console (not shown) of the line control unit 22. The line control unit 22 successively transmits together with a test instruction signal the testing subscriber number and ID number to the testing fixed station 33 via the monitoring control unit 24, the monitoring control line 61 and the monitoring control unit 32. Each mobile station 4 has an independent subscriber number and ID number assigned thereto which are different from those assigned to other mobile stations 4. The testing subscriber number and ID number are set different from those already assigned to the mobile stations 4.
The testing fixed station 33 uses the testing subscriber number and ID number, which are received via the monitoring control line, to call out a control channel of a radio line between the testing fixed station 33 and the radio unit 31. Hence, a line is connected between the testing fixed station 33 and the line control unit 22. When the call out of the control channel is received, the radio unit 31 informs the line control unit 22 that the call out is received. The line control unit 22 detects the testing subscriber number and ID number which are set from the call information. It is possible to detect whether or not the control channel is functioning correctly and to confirm whether or not a line is connected between the line control unit 22 and the testing fixed station 33 based on the detected testing subscriber number and ID number.
The call out of the control channel from the testing fixed station 33 is made periodically. As a result, the abnormal/normal state of the line between the mobile station 4 and the line control unit 22 is monitored periodically.
In the conventional mobile communication system such as the portable mobile radiophone system described above, the line control unit 22 transmits the test instruction information to testing fixed station 33 via the monitoring control line 61. For this reason, when a fault such as a disconnection of the line of the monitoring control system occurs, it no longer becomes possible to make the periodic call out from the testing fixed station 33 to the control channel. There is a problem in that it becomes impossible to carry out a monitoring such as detecting a fault in the message line.